$ { {3} \times \left[\begin{array}{rr}{3} & {2} \\ {3} & {1}\end{array}\right] = {?} } $
Solution: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{3}\times{3} & {3}\times{2} \\ {3}\times{3} & {3}\times{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{9} & {6} \\ {9} & {3}\end{array}\right]}$